For a long time, fructose has been referred to as “fruit sugar”, which gave it, by association, a certain image of healthy sugar. In addition, it was the type of sugar recommended for diabetics, because it hardly raised insulin levels.
Do we get fat because the body thinks it has to survive the winter?
However, in recent years, fructose has shown its darker face, largely because its effect on metabolism and the brain has been discovered. Also, because the consumption of fructose, through the common sugar of which it is a part, has skyrocketed throughout the world, with very negative consequences for health.
A cheated gift
Plants do not offer their fruits because they have a generous heart, but because they care. Animals, especially mammals and birds, eat the fruits and spread the seeds. To attract animals, the fruits are brightly colored and contain sugar, easy energy.
The simplest sugar is glucose, but the problem is that when an animal (us included) eats enough glucose, gets full and stops eating. That’s why the sweet gift of plants has a catch: fructose.
The fructose has the effect of deactivating the appetite control mechanismsmuch more than glucose. On the one hand, it makes cells resistant (“deaf”) to leptin, the satiety hormone, and on the other hand, it increases the levels of ghrelin, the hunger hormone. The result is that we do not stop eating.
On the other hand, fructose induces insulin resistance. In fact, in the laboratory turns rats into “diabetics” with a fructose diet in just three months. Having insulin resistance means that cholesterol and triglycerides in the blood increase, and there is a greater accumulation of fat in the body.
As if that weren’t enough, most of the calories from fructose are converted to fat. Fructose is processed in the liver, where it may be converted to glucose to replenish the liver’s own glycogen stores. However, these reserves are usually full because we eat bread, pasta and potatoes every day, which are sources of glucose. With full reserves, all of the fructose is transformed into triglycerides, that is, the effect of fructose is the same as eating fat.
Fructose, the microbiota and the brain
Also, by taking concentrated fructose in large amounts (which is what happens every time we eat foods with sugar or fruit juices) changes the composition of the intestinal microbiota, in this case for the worse. They increase the bacteria that induce obesity and decrease those that protect the intestine wall and have anti-inflammatory functions. This increases intestinal permeability and produces inflammation.
Finally, fructose also has effects on the brain. Fructose induces insulin resistance in neurons, so they cannot absorb as much energy from glucose. This affects memory and mental abilitiesand inhibits the formation of new neurons in the hypothalamus.
All this could make us think that nature is conspiring against us. Plants offer us fruit poisoned with a substance, fructose, which makes us eat without measure, gain weight, become resistant to insulin and a bit silly.
However, there was a time when all this was beneficial. Fruit (and honey, another source of fructose) were only available at the end of summer, and at that time it was a good idea to store up body fat to survive the winter.
Today, however, we have access to the fruit throughout the year. Common sugar, present in almost all processed foods, contains 50% fructose, or more, in the case of corn syrup. The same goes for natural substitutes that are presented as better than sugar and are actually sugar. The previously temporary hijacking of our body by fructose, and an exchange of favors between plants and animals, has become a permanent state for many human beings, and it is affecting health.
Interestingly, the negative effects on the microbiota only occur with refined sugars, not with the consumption of whole fruit pieces. The explanation seems to be that fruits do not only have sugars. On the one hand, the fiber in the fruit is satiating and counteracts the effects of fructose. In addition, especially in their skin and seeds, fruits contain different substances that they use as a defense against insects and other pests, many of which are antioxidants such as anthocyanins and vitamin C.
These substances are responsible for the fruit’s beneficial health effects, which occur despite the sugar they contain. But keep in mind that the same benefits can be obtained from vegetables.
What is all this based on?